Returns the estimated maximum distance which the layer style will bleed outside
the drawn shape when drawn in the specified /a context. For example, polygons
drawn with an stroke will draw half the width
of the stroke outside of the polygon. This amount is estimated, since it may
be affected by data defined symbology rules.*

Returns the units to use for sizes and widths within the symbol layer. Individual
symbol layer subclasses will interpret this in different ways, e.g., a marker symbol
layer may use it to specify the units for the marker size, while a line symbol
layer may use it to specify the units for the line width.

Sets the units to use for sizes and widths within the symbol layer. Individual
symbol layer subclasses will interpret this in different ways, e.g., a marker symbol
layer may use it to specify the units for the marker size, while a line symbol
layer may use it to specify the units for the line width.